Impact of biofilm‐induced heterogeneities on solute transport in porous media

Abstract

In subsurface systems, biofilm may degrade organic or organometallic pollutants contributing to natural attenuation and soil bioremediation techniques. This increase of microbial activity leads to change the hydrodynamic properties of aquifers. The purpose of this work was to investigate the influence of biofilm-induced heterogeneities on solute transport in porous media and more specifically on dispersivity. We pursued this goal by (i) monitoring both spatial concentration fields and solute breakthrough curves from conservative tracer experiments in a biofilm-supporting porous medium, (ii) characterizing in situ the changes in biovolume and visualizing the dynamics of the biological material at the mesoscale. A series of experiments was carried out in a flow cell system (60 cm 3 ) with a silica sand (U 5 50-70 mesh) as solid carrier and Shewanella oneidensis MR-1 as bacterial strain. Biofilm growth was monitored by image acquisition with a digital camera. The biofilm volume fraction was estimated through tracer experiments with the Blue Dextran macromolecule as in size-exclusion chromatography, leading to a fair picture of the biocolonization within the flow cell. Biofilm growth was achieved in the whole flow cell in 29 days and up to 50% of void space volume was plugged. The influence of biofilm maturation on porous medium transport properties was evaluated from tracer experiments using Brilliant Blue FCF. An experimental correlation was found between effective (i.e., nonbiocolonized) porosity and biofilm-affected dispersivity. Comparison with values given by the theoretical model of Taylor and Jaff e (1990b) yields a fair agreement.

Pore‐Scale Hydrodynamics in a Progressively Bioclogged Three‐Dimensional Porous Medium: 3‐D Particle Tracking Experiments and Stochastic Transport Modeling

“…For instance, they showed that the variance of velocity distributions increased more slowly in 3‐D than in 2‐D and the formation of preferential flow pathways was strongly delayed in 3‐D, warranting experimental data to corroborate the findings. Ultimately, biofilms were shown to cause an increase of non‐Fickian transport dynamics (Knecht et al, ; Kone et al, ; Seymour et al, ).…”

Reactive Transport: A Review of Basic Concepts with Emphasis on Biochemical Processes

“…Maybe the most interesting is the effect of biofilm growth on transport properties, such as, dispersivity and parameters for the porewater-biofilm exchange, which in their turn effect biochemical reactions and biofilm growth [231]. Experimental results have demonstrated that, indeed, biofilm growth induces heterogeneities that affect the transport in porous media [232,233]. Moreover, it forms preferential flow paths and stagnation zones [230].…”

Non-Invasive Measurement, Mathematical Simulation and In Situ Detection of Biofilm Evolution in Porous Media: A Review

“…Table 1 lists the porous materials and the relevant grain sizes. [55] 500-1500 Clay beads [20] >1000 Nafion pellets [56] 2500 Transparent Nafion pellets [57] 2500 NMR Glass beads [58] 1000-1500 Monodisperse beads [39] 241 Monodisperse beads [59] 241 Glass beads [60] 100 Soil [61] -CLSM Glass beads [62] 425-600 CCD Silica sand [63] 210-297…”

“…In addition to the above methods, an optical method was tried in terms for realizing a nondestructive monitor of bioclogging on a time scale. Kone et al [63] designed a transparent glass flow unit loaded with quartz sand (internal volume 10 cm × 10 cm × 0.5 cm) to visualize the plug caused by biomass growth through imaging acquisition with a chargecoupled device (CCD) camera. The effect of biomass growth on mass transport in a porous media was studied by a tracer experiment through visible light transmission method.…”